Transcriptional repressor NF-X1 is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 that in humans is encoded by the NFX1 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

MHC class II

MHC class II

MHC Class II molecules are found only on a few specialized cell types, including macrophages, dendritic cells and B cells, all of which are professional antigen-presenting cells ....

 gene expression is controlled primarily at the transcriptional level by transcription factor

Transcription factor

In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...

s that bind to the X and Y boxes, two highly conserved elements in the proximal promoter of MHC class II genes. The protein encoded by this gene is a transcriptional repressor

Repressor

In molecular genetics, a repressor is a DNA-binding protein that regulates the expression of one or more genes by binding to the operator and blocking the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes. This blocking of expression is called...

 capable of binding to the conserved X box motif of HLA-DRA

HLA-DRA

HLA class II histocompatibility antigen, DR alpha chain is a protein that in humans is encoded by the HLA-DRA gene. HLA-DRA encodes the alpha subunit of HLA-DR. Unlike the alpha chains of other Human MHC class II molecules, the alpha subunit is practically invariable...

 and other MHC class II genes in vitro. The protein may play a role in regulating the duration of an inflammatory response by limiting the period in which class II MHC molecules are induced by IFN-γ

Interferon-gamma

Interferon-gamma is a dimerized soluble cytokine that is the only member of the type II class of interferons. This interferon was originally called macrophage-activating factor, a term now used to describe a larger family of proteins to which IFN-γ belongs...

. Three alternative splice variants

Alternative splicing

Alternative splicing is a process by which the exons of the RNA produced by transcription of a gene are reconnected in multiple ways during RNA splicing...

, each of which encodes a different isoform

Protein isoform

A protein isoform is any of several different forms of the same protein. Different forms of a protein may be produced from related genes, or may arise from the same gene by alternative splicing. A large number of isoforms are caused by single-nucleotide polymorphisms or SNPs, small genetic...

, have been identified.